1. Field of the Invention
This invention relates to a film winding device for a camera.
2. Description of the Prior Art
Heretofore there have been known various film winding devices of the kind called spool drive type which transmit a driving force to a spool to feed the film and also rotate a sprocket through the medium of the film being fed in such a manner that the photo taking mechanisms of the camera such as an automatic focusing mechanism, a shutter mechanism, etc. are charge while the film is fed to a prescribed extent. Compared with winding devices of another kind called sprocket drive type, the spool drive type winding device can be arranged in a simple structure highly suitable for small cameras such as the lens shutter type camera. However, a disadvantage of the device of this type arises in that since the spool drive type winding device has a sprocket arranged to be rotated by the film being fed, it is incapable of charging the photo taking mechanism when the camera is not loaded with film. In such an instance, therefore, the spool drive type device does not permit testing the shutter, the automatic focusing mechanism, etc. Besides, with no film loaded, a winding stop mechanism which is arranged to stop the winding action every time one frame portion of the film has been fed does not operate and thus would result in an incessant operation of a motor in cases where a winding action is arranged to be accomplished by the driving force of a motor or the like.
Particularly, in the case of a camera having an automatic loading mechanism which performs film winding by bringing the force end of the film into contact with the periphery of a spool and by having the film wound round the spool by virtue of a frictional force is such a manner as disclosed, for example, in U.S. Pat. No. 3,567,147, the device is arranged not to have the film wound up with the back cover of the camera left open. In such a case, therefore, if the winding action is allowed to begin with the back cover left open at the time of film loading, electric power would be wastefully consumed with the spool continuously rotated by the motor.
To solve the above-stated problem, it is conceivable to arrange a winding device of the spool driving type in a manner wherein a drive source is connected to a sprocket through a one-way clutch in the winding device. When the sprocket is rotated by the feeding movement of the film, the output shaft of a one-way clutch which operates in response to the sprocket is arranged to rotate faster than the input shaft of the one-way clutch arranged to have the driving force of the drive source transmitted directly thereto. The one-way clutch is thus arranged to be in a non-transmissive state and the sprocket to be rotated by the film during film winding. In cases where the film is not loaded, the one-way clutch is brought into a transmissive state to have the driving force transmitted directly to the sprocket to cause the sprocket to be rotated thereby. However, a device based on that concept inevitably results in inconvenience, because the conventional one-way clutch is arranged to be switched over between the transmissive and non-transmissive states according to the speed of the output shaft relative to that of the input shaft thereof.
With that device employed, when the film is rewound, the output shaft which operates in response to the rotation of the sprocket rotates in a direction opposite to its rotating direction for film winding. Therefore, this brings the one-way clutch into a transmissive state. As a result of this, the drive source which is connected to the input shaft acts restrictively on the film rewinding operation. The restrictive action of the drive source inhibits the film rewinding operation from being accomplished at a high speed. Besides, such rewinding tends to damage the film as the film is pulled by the sprocket and by a fork provided on the rewinding side.